1. Field of Invention
The present invention relates to a fan and in particular to a fan and an airflow guiding structure thereof that can change the direction of the airflows of the fan.
2. Related Art
Since the performance of the electronic apparatuses has been improved, the heat dissipation device or system becomes one of the indispensable equipments of the electronic apparatuses. If the heats generated by the electronic apparatus can not be dissipated properly, the performance thereof may become worse and, even more the electronic apparatus may be burnt out. As for the micro electronic devices such as the integrated circuits (ICs), the dissipation device is much more important. In view of the integrated density of the ICs being increasing and the progress of the packaging technology, the size of the ICs becomes smaller, and the heat accumulated in per unit area of the integrated circuits become higher. Therefore, a heat dissipation device with high heat dissipation efficiency has become one of the most important development areas in the electronic industry.
Fan is the most popular heat dissipation device in the present heat dissipation technology. According to the directions of the airflow entering and exiting from the fan, the fan can be classified to axial-flow fans and centrifugal fans. In an axial-flow fan, the airflow enters the conventional axial-flow fan through the inlet and then exits through the outlet. The airflow direction entering into the inlet is roughly parallel to the airflow direction exiting from the outlet. On the other hand, in a centrifugal fan, the airflow enters the conventional centrifugal fan through the inlet and then exits through the outlet. The airflow direction entering into the inlet is roughly perpendicular to the airflow direction exiting from the outlet. Compared to the axial-flow fan, although the centrifugal fan can change the airflow direction, the centrifugal fan has the drawbacks of lower performance, lower airflow quantity and louder noise. Moreover, the centrifugal fan is hard to provide a multi-function fan in the current trend towards small size.